The most common artificial leg for below knee amputees is of a rigid nature. A solid shank will connect the socket, which mounts the artificial leg to the residual limb of the amputee, and the artificial foot. The shank is often made out of a rigid alloy, such as one containing titanium or from shaped wood. The energy storing system can take the shape of a C-shaped plastic spring running from the ankle through the arch terminating towards the ball of the foot. In the case of the metal shank artificial leg, a system of this type can weigh in the range of 21/2 to 4 pounds. In the case of the wood shank, the artificial leg can weigh on the order of 3 pounds.
The Flexfoot.RTM. artificial leg produced by Flexfoot, Inc., Irvine, Calif. is an example of a currently available artificial leg which exhibits a more natural dynamic action by using a flexible energy storing pylon and keel, the flexible pylon and keel being formed from a strip of laminated reinforced composite which is mechanically attached to the socket descending down to form the pylon and continuing on to form the keel of the artificial leg. Applying pressure to the Flexfoot.RTM. artificial leg (e.g. walking on it) causes flexation of the pylon and foot which acts as a spring to store energy which is also released during walking or running movement. While the Flexfoot.RTM. artificial leg allows for more natural feeling movement due to its energy storing and returning action than prior rigid artificial legs, and although the Flexfoot weighs the same as other prior artificial legs made of titanium and/or wood, its weight can be of concern to geriatric patients. The Flexfoot is also not recommended for patients with low to moderate activity levels, because of the weight and cost.
Advances in the art have also included a continuous one piece prosthesis, such as that shown in U.S. Pat. No. 5,219,360. That prosthesis offers the advantages of lightweight and improved energy storage and release characteristics. That one piece prosthesis can, however, require multiple trips to the prosthetist for fitting. In certain cases the patient may have to be fitted with another prosthesis which will be adjusted for height, pylon length, inversion, eversion, etc. Once the prosthesis is adjusted, the measurements from the adjusted prosthesis are then used to form the one piece prosthesis. This may require more than one trip to the prosthetist. Further, once the prosthesis is manufactured, adjustments may require reheating and reforming material.